This invention relates to face masks, and is specifically directed to an improved means for warming cold air prior to inhalation by a mask user.
Inhaling cold air into the respiratory tract can be detrimental to the health of persons suffering from emphysema, asthma, angina and various other ailments. In cold weather, persons suffering from such ailments must either avoid breathing cold air altogether or take precautions to heat cold air before it is breathed. In addition, persons of good health working and exercising in frigid climates must take precautions against excessive heat loss due to the inhalation of frigid air.
A variety of apparatuses have been employed in the past to overcome the ill effects of breathing cold air. These range from simple scarfs to complex breathing masks and are employed to preheat cold air before inhalation. Most of these devices, however, either do not sufficiently preheat the cold surrounding air before breathing or are complex, cumbersome and prohibitively expensive. Several such breathing apparatuses are disclosed in the following patents: U.S. Pat. Nos. 4,150,671; 4,601,287; and 4,620,537. These mask apparatuses attempt to preheat air with battery powered heating elements or heat exchange devices. However, existing masks with heating elements have been inconvenient to use under normal use conditions because large, poorly located battery power supplies are either separate from the mask and require additional means for transport or are located within the mask breathing space where the battery is exposed to high moisture levels and where a user would be subjected to dangers from battery corrosion or battery fumes.
Another problem experienced with existing masks having heating elements is that a large amount of power is required to directly heat cold surrounding air. There have been attempts to reduce mask heating element power requirements by passing inhaled and exhaled air through heat absorbing material so as to preheat incoming air with heat stored from exhaled air before the incoming air reaches the heating element. However, these designs have the problems that some previously exhaled air is inhaled again and that exhaled air passes across the heating element where it is heated before being exhausted to the surrounding atmosphere.
In the mask disclosed in U.S. Pat. No. 4,150,671, air is preheated with a complex heat exchanger device having separate intake and exhaust passages rather than with a heating element. Thus, the problem of rebreathing exhaled air is overcome, but the heat exchange device is so complex that it cannot be economically manufactured. It is also difficult for such exchangers to sufficiently heat frigid air.